Silencing the cochaperone CDC37 destabilizes kinase clients and sensitizes cancer cells to HSP90 inhibitors.
The cochaperone CDC37 promotes the association of HSP90 with the protein kinase subset of client proteins to maintain their stability and signalling functions. HSP90 inhibitors induce depletion of clients, which include several oncogenic kinases. We hypothesized that the targeting of CDC37 using siRNAs would compromise the maturation of these clients and increase the sensitivity of cancer cells to HSP90 inhibitors. Here, we show that silencing of CDC37 in human colon cancer cells diminished the association of kinase clients with HSP90 and reduced levels of the clients ERBB2, CRAF, CDK4 and CDK6, as well as phosphorylated AKT. CDC37 silencing promoted the proteasome-mediated degradation of kinase clients, suggesting a degradation pathway independent from HSP90 binding. Decreased cell signalling through kinase clients was also demonstrated by reduced phosphorylation of downstream substrates and colon cancer cell proliferation was subsequently reduced by the inhibition of the G1/S-phase transition. Furthermore, combining CDC37 silencing with the HSP90 inhibitor 17-AAG induced more extensive and sustained depletion of kinase clients and potentiated cell cycle arrest and apoptosis. These results support an essential role for CDC37 in concert with HSP90 in maintaining oncogenic protein kinase clients and endorse the therapeutic potential of targeting CDC37 in cancer.
Smith
J R
JR
Signal Transduction and Molecular Pharmacology Team, Cancer Research UK Centre for Cancer Therapeutics, The Institute of Cancer Research, Haddow Laboratories, Surrey, UK.
Clarke
P A
PA
de Billy
E
E
Workman
P
P
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones / Q000494:pharmacology; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D018833:Chaperonins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D018390:Gene Targeting; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008297:Male; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011720:Pyrazoles / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
D016227:Benzoquinones; C498362:CDC37 protein, human; D018797:Cell Cycle Proteins; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D009363:Neoplasm Proteins; D011720:Pyrazoles; D034741:RNA, Small Interfering; C520150:VER-49009; C112765:tanespimycin; D011494:Protein Kinases; D046988:Proteasome Endopeptidase Complex; D018833:Chaperonins